Fix fd leaks on device nodes

fs/fake.c

@@ -498,6 +498,7 @@ const struct fs_ops fakefs = {
     .symlink = fakefs_symlink,
     .mknod = fakefs_mknod,
 
+    .close = realfs_close,
     .stat = fakefs_stat,
     .fstat = fakefs_fstat,
     .flock = realfs_flock,

fs/fd.c

@@ -41,6 +41,12 @@ int fd_close(struct fd *fd) {
         unlock(&fd->poll_lock);
         if (fd->ops->close)
             err = fd->ops->close(fd);
+        // see comment in close in kernel/fs.h
+        if (fd->mount->fs->close && fd->mount->fs->close != fd->ops->close) {
+            int new_err = fd->mount->fs->close(fd);
+            if (new_err < 0)
+                err = new_err;
+        }
         free(fd);
     }
     return err;
@@ -241,8 +247,7 @@ dword_t sys_dup2(fd_t f, fd_t new_f) {
     if (err < 0)
         return err;
     f_close(new_f);
-    fd->refcount++;
-    table->files[new_f] = fd;
+    table->files[new_f] = fd_retain(fd);
     return new_f;
 }
 

fs/fd.h

@@ -20,10 +20,6 @@ struct fd {
 
     // fd data
     union {
-        // realfs/fakefs
-        struct {
-            DIR *dir;
-        };
         // proc
         struct {
             struct proc_entry proc_entry;
@@ -55,8 +51,8 @@ struct fd {
 
     // fs/inode data
     struct mount *mount;
-    // seeks on this fd require the lock
-    int real_fd;
+    int real_fd; // seeks on this fd require the lock
+    DIR *dir;
     struct statbuf stat; // for adhoc fs
 
     // these are used for a variety of things related to the fd

fs/real.c

@@ -425,6 +425,7 @@ const struct fs_ops realfs = {
     .symlink = realfs_symlink,
     .mknod = realfs_mknod,
 
+    .close = realfs_close,
     .stat = realfs_stat,
     .fstat = realfs_fstat,
     .setattr = realfs_setattr,

kernel/fs.h

@@ -133,6 +133,12 @@ struct fs_ops {
     int (*symlink)(struct mount *mount, const char *target, const char *link);
     int (*mknod)(struct mount *mount, const char *path, mode_t_ mode, dev_t_ dev);
 
+    // There's a close function in both the fs and fd to handle device files
+    // where, for instance, there's a real_fd needed for getpath and also a tty
+    // reference, and both need to be released when the fd is closed.
+    // If they are the same function, it will only be called once.
+    int (*close)(struct fd *fd);
+
     int (*stat)(struct mount *mount, const char *path, struct statbuf *stat, bool follow_links);
     int (*fstat)(struct fd *fd, struct statbuf *stat);
     int (*setattr)(struct mount *mount, const char *path, struct attr attr);